mandela changed. gandhi changed. all the great leaders, ♪ >> narrator: in february last year, pope benedict stunned the world by being the first pope to resign in 600 years. >> no person has had more influence on the life of the church, how it works on the inside, than joseph ratzinger. and he gave it up. >> narrator: when the helicopter took him away, benedict was leaving behind a bitterly divided vatican. this is the inside story of the events that undermined his papacy. it's a story of corruption and cover-up. >> if i don't get a response from you, i'll go public.